This invention relates generally to article imprinting apparatus for imprinting information upon packages, cartons and the like as they travel successively spaced along the reach of a conveyor. Moreover, there is provided an improved reciprocable imprinting apparatus which is durable and versatile, less costly to fabricate, assemble and maintain than prior devices, which enables the employment of pre-inked ink cartridges, which markededly increases the useful life thereof by having means for effecting sealing off of the cartridges during all but the actual imprinting stroke of the apparatus.
In particular, the apparatus provided by the invention includes an imprinting head carrying a biased releasably mounted type holder on which type font can be secured. An effective seal is established between the imprinting head and a disposable inking cartridge to prevent evaporative loss from the cartridge, except during the momentary translation of the head along a path leading to an angularly displaced imprinting location whereat the imprinting is performed. Drive means including a drive linkage, and cam and follower guide means are provided to direct the imprinting head along said path in imprinting and return strokes wherein the head is driven at a constant angular rotational accelleration to midstroke whereat a constant rate of decelleration is effected until the end of the stroke.
Known devices capable of imprinting information upon surfaces of packages, cartons and the like conveyed spaced along a given path along the reach of the conveyor generally are of complex construction with accompanying expense of manufacture, fabrication, assembly and maintenance. Two major types of devices are employed in imprinting indicia on packages and the like. One type of device includes a rotary imprinting wheel on which the type font can be mounted for repeated inking by rotary ink transfer means to which ink is supplied from a source thereof, the imprinting wheel intercepting the article to be imprinted. The second major type of imprinting apparatus involves stamping or impacting inked type face means repeatedly upon successively arriving articles. The invention concerns the latter type.
The type face means are supplied with ink by impacting upon an ink saturated pad or the like, usually supplied by some storage means such as a cartridge or the like, which include an ink impervious body having an access window.
The invention herein is concerned with the repeatable impact type imprinting apparatus which involves substantial frequency of required maintenance, and particularly the short life of the inking means employed. Frequent and time-consuming ink cartridge replacement is the rule. One reason for such short cartridge useful life may be attributed to the unusually fast drying character of the ink employed. These highly volatile inks evaporate rapidly, usually depleting the ink pad after only a short time or leaving an inking surface which quickly becomes hard and dry, preventing the normal capillarity effect to resupply the surface of the pad. This phenomenon is encountered where the ink supply takes the form of an ink-saturated absorbent pad disposed within a disposable cartridge having access window means to accommodate the printing head. Often, the skin formed by solvent evaporation is hard whereby ink is unevenly applied to the type font, or at least, is insufficient to effect uniform marking of the package, etc.
During the course of the operation of the imprinting apparatus, the imprinting head is disposed substantially longer at the rest condition, engaged against the inking pad surface. The translation of the imprinting head to the imprinting location and application of the imprint occupies minimal time and requires little exposure of the inking pad. Nevertheless, substantial reduction of the effectiveness of the inking means results since evaporation, etc. occurs while the type holder (carried by the imprinting head) is engaged with the inking pad of the ink storing cartridge.
Seals have been attempted with mixed results. Some attempts have interfered with the inking of the type font while others have been ineffective, failing to establish an effective seal.
It should be noted that the ink-saturated pad is generally resilient because of its saturated condition and the character of the ink absorbent material used to form the pad. The area of engagement of the imprinting head as well as the surface of the head engaging the pad is sometimes so resilient as to fail to establish an effective seal. The type holder seated on the imprinting head and effectively constituting same also is not well suited to make a proper seal with the ink-saturated pad or its surrounding border defining lining member, where provided. Accordingly, rapid evaporation of the fast drying ink still materially reduces the useful life of available cartridges requiring removal of the exhausted cartridge and replacement with a fresh cartridge. Often such premature disabling of the ink supply cartridges occurs many times during a normal (average) imprinting run regardless of the number of articles imprinted.
Another problem encountered with the employment of imprinting apparatus of the type described hereinabove involves the formation of a hard skin formed on the pad as a result of evaporation. The skin prevents transfer of ink from the pad, even though there is substantial ink remainent within the impregnated storing pad. This results in premature removal and replacement of the cartridge long prior to depletion of the ink stored therein.
Still another difficulty encountered with an imprinting apparatus such as described above involves the means employed to effect the translation of the imprinting head to the imprinting position and return. It is known to employ pivotable arms and the like to mount an imprinting head for repeated movement. Ordinarily, these arms are coupled to a source of dynamic power, such as a fluid operated hydraulic or pneumatic system coupled through a signalling device to a drive arms, in turn secured to an imprinting head and/or to the mounting therefor. Known drives cause the imprinting head to be translated from its rest condition to its angularly displaced position at the imprinting location, so that the imprinting head assumes an orientation with its center line perpendicular to the surface upon which imprinting is to be effected.
It is difficult to maintain the head in the proper path to prevent deviation therefrom during translation to and return from the imprinting location. There has been considerable difficulty in achieving the proper orientation of said imprinting head as well as in controlling the contact pressure exerted by the imprinting head both upon the package surface and upon the inksaturated pad. Shaking and misalignment have been experienced. Where the contact pressure at impact is too great, smearing and/or other blurring of the imprint would be encountered. Often the imprinting head would be misoriented during its imprinting contact with the package surface, resulting in partial imprints, or imprints carrying too much ink, notwithstanding the fast drying nature of the inks employed. The return stroke often strongly impacts in the relatively soft, yieldable surface of the ink-saturated pad whereby to cause splashing of ink fouling the apparatus, the imprinting head and carrier therefor, and often causing ink to be thrown outward, fouling the ambient surroundings.
The imprinting apparatus proposed in the referenced application has been effective to prevent the above adverse occurances and includes, as a part thereof, means to prevent evaporative loss by establishing an effective sealed engagement between the ink cartridge and the printing head during all but the actual imprinting. Additionally, the impact or contact pressure exercised by the imprinting head (the type face carried thereby) upon the saturated inking pad is controlled so that one need not be forced to elect between a contact pressure at impact sufficient to assure proper inking and reduction of contact pressure to prevent splashing of ink.
The apparatus therein also provided for control of the quantity of ink applied to the type font during each inking step, to alleviate the problem of excess ink applied to the type which results in smearing of the imprint and the problem of unsatisfactory faint imprints resulting from insufficient application of ink. Additionally, the force of impact upon the surface to be imprinted is carefully controlled to assure proper clear and sharply defined imprints without requiring controls.
The translation of the imprinting head between the pair of angularly displaced operating positions was effected by mechanisms which are relatively simple in construction and are effective to assure proper orientation of the type carried by the imprinting head both on the ink saturated pad during the rest condition, and during the time period when momentarily displaced therefrom to effect application of the imprint. Facility in servicing the imprinting apparatus also was a desirable feature not readily available with earlier imprinting devices of this type. Advantages of the removability both of the inking cartridge and of the type holder for replacement, change or reorientation were achieved which is a strong factor in employing the apparatus of said referenced application.
The imprinting apparatus described in said referenced application included an imprinting head carrying type font seated upon a support member and arranged for displacement between a pair of angularly spaced positions (by a signal controlled drive device, either fluid operated or electrically operated). The imprinting head thus intermittently was displaced form a rest position to an imprinting position at which the type holder momentarily contacts the surface to be imprinted. In the rest position, the head is in sealed engagement with an apertured closure of a pre-inked ink storing cartridge so as to seal the cartridge while the imprinting head is coated with ink from an ink-saturated pad within the cartridge. The cartridge was yieldably held in position in a mounting disposed in said apparatus so that a desired contact pressure between the imprinting head in its rest position and the saturated pad is maintained so as to effect efficient ink transfer to the imprinting head.
The pre-inked cartridge includes an ink saturated pad seated within an ink impervious housing, usually formed of plastic material. Access is enabled to one side of the cartridge by removal of cover piece leaving an ink impervious border portion surrounding the window exposed when the cover is removed. The imprinting head seats on the inner rim of a disk-shaped mask seated on the ink cartridge, said mask itself being seated upon a plastic border portion, when the head is at the rest position to effect a seal therebetween to control thereby the impact of the imprinting head upon said ink-saturated pad reducing the contact pressure at impact which otherwise would cause splash and further, to prevent excessive impact and contact pressure between the returning imprinting head and the saturated ink pad. Means also are provided to facilitate removal and/or replacement of the type holder of the imprinting head without causing undue downtime of the apparatus. The control of contact pressure is effective for both the inking and the imprinting states of the imprinting head. Means also to cushion the impact of the imprinting head are provided so that the imprinting head effects a soft impact with the surface of the ink-saturated pad and with the surface of the article to be imprinted, respectively.
The path taken by the imprinting head of said referenced application was controlled by a pair of linkages secured to the head, including a direct driven link pair and a follower or idler linkage pair. The imprinting head at its rest or loading condition is oriented at a ninety degree angle relative horizontal. The head is driven through a path toward an offset printing location angularly rotating through 90' in the course of its simultaneous movement to its imprinting location. The idler link provided by the referenced structure follows a path whereby the angular rate of rotation decreases until the mid point of the path is reached and then increases until the terminus of its printing stroke is reached. The type holder is spring biased so that it is inertially driven outward of the head on the sudden cessation of movement of the imprinting head at the imprinting terminus of said path.
Occasionally, the movement of the imprinting head through the imprinting stroke angularly is misdirected so that the orientation of the type holder may be misoriented at the impact location. The head also may be held up at the mid-point of travel, misoriented, inverted, or simply stuck thereat as the rate of travel and the angular rotation, ie., the whip--is at its least. A resilient bumper is suggested in the referenced application to aid in guiding the rotating imprinting head in following the proper path.
While normally the operation of the drive and guide means provided by the referenced apparatus is successful, improvement of its apparatus and reliability is desirable but without any loss in advantage gained by said apparatus over other apparatus.
Another improvement desired over the referenced apparatus is to provide for adjustment of the imprint distance relative to article being imprinted so that the installation (mounting) of the imprinting apparatus need not be changed (raised or lowered) to compensate for small changes in height of the articles.